The invention concerns a method for the continuous casting of slabs, thin slabs, blooms, preliminary sections, rounds, tubular sections, billets, and the like from molten metal in a continuous casting plant, where metal flows vertically downward from a mold, where the metal strip is then guided vertically downward along a vertical strand guide, cooling as it moves, where the metal strip is then deflected from the vertical direction to the horizontal direction, and where in the terminal area of the deflection of the metal strip into the horizontal direction or after the deflection into the horizontal direction, a mechanical deformation of the metal strip is carried out. The invention also concerns a continuous casting installation, especially for carrying out this method.
A continuous casting method of this general type is disclosed, for example, by EP 1 108 485 A1 and WO 2004/048016 A2. In this method, molten metal, especially steel, is discharged vertically downward from a mold. As it flows down, it solidifies and forms a metal strip, which is gradually deflected or turned from the vertical direction to the horizontal direction. Directly below the mold, there is a vertical strand guide, which initially guides the still very hot metal strip vertically downward. The metal strip is then gradually turned into the horizontal direction by suitable rolls or rollers. Once the strip is moving horizontally, it is usually subjected to a straightening process, i.e., the metal strip passes through a straightener, in which it is mechanically deformed.
Similar solutions are described in JP 63 112058 A, WO 03/013763 A, EP 0 611 610 A1, DE 22 08 928 A1, DE 24 35 495 A1, DE 25 07 971 A1, EP 0 343 103 A1, EP 1 243 343 B1, EP 1 356 868 B1, and EP 1 366 838 A.
Great importance is attached to the cooling of the metal strip after it emerges from the mold. In this connection, EP 1 108 485 A1 proposes a device for cooling the cast strand in a cooling zone, in which the strand is supported and guided by pairs of rollers arranged one above the other transversely to the axis of the strand along the strand discharge direction, with the strand being further cooled by the discharge of coolant. To achieve efficient cooling of the metal strip, the proposed device comprises a cooling element that conveys coolant and is arranged between two rollers positioned one above the other. The cooling element extends along the longitudinal axis of the rollers and is designed in such a way that gaps are formed between the given cooling element and the roller and between the cooling element and the strand. Each cooling element is provided with at least one channel that conveys coolant and opens into a gap.
To achieve optimum temperature management of the cast metal strip, WO 2004/048016 A2 proposes that a dynamic spraying system in the form of the distribution of the amount of water and the pressure distribution or pulse distribution over the width and length of the strand is functionally controlled by means of the runout temperature, which is determined by monitoring the surface temperature at the end of the metallurgical length of the cast strand, so as to obtain a temperature curve calculated for the strand length and the strand width.
Many other solutions to the problem likewise deal with the question of how a metal strand can be cooled efficiently and in a way that is suitable from the standpoint of the process engineering that is involved. In this regard, reference is made to JP 61074763 A, JP 9057412, EP 0 650 790 B1, U.S. Pat. No. 6,374,901 B1, US 2002/0129921 A1, EP 0 686 702 B1, WO 01/91943 A1, JP 2004167521, and JP 2002079356.
It has been found that in addition to cooling of the cast metal strand that is efficient and suitable from the standpoint of the process engineering, high-temperature oxidation or scaling of the metal strip plays a considerable role. Due to the very high temperature of the metal strip immediately after the metal has been discharged from the mold, the strip is subject to an intense scaling effect, which adversely affects especially the downstream process steps. Therefore, it is important to try to keep the degree of scaling as low as possible.